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Question
What part of the heart's conduction system acts as the primary pacemaker?
A. SA node
B. AV node
C. Bundle of His
D. Purkinje fibers
Answer
This answer is hidden. It contains 1 characters.
Related questions
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The Leydig cells of the testes constitute a blood-testis barrier that prevents autoimmune destruction of the sperm.
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C. high concentrations of testosterone.
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Women do not enter a refractory period following orgasm and are capable of multiple orgasms.
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Which of the following is a precursor to melatonin synthesis?
A. tryptophan
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B. regression of the wolffian ducts during embryonic development.
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The role of melatonin in puberty of humans is well established and critical.
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Pubic and axillary hair growth at puberty is from increased secretion of
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C. androgens from the adrenal cortex.
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Epiphyseal growth in males is stimulated by estrogen.
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The rate at which GnRH is secreted from the hypothalamus determines whether LH or FSH is secreted from the anterior pituitary.
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A male with 5 alpha-reductase deficiency will have male internal sex organs but more female appearing external genitals.
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Males lacking testosterone receptors would
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Treating a male fetus with antibodies to DHT would prevent development of the epididymides.
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Female accessory sex organs develop from the mesonephric ducts.
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How many chromosomes are found in a normal human cell?
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B. 23 pair
C. 46
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Cryptorchid males do not produce testosterone.
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What hormone is secreted by the anterior pituitary that stimulates production of milk proteins?
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Genetic screening of newborns using only a drop of blood can determine which of the following genetic disorders?
A. hypothyroidism
B. cystic fibrosis
C. sickle cell anemia
D. All of the choices are correct.
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What hormone may play a role in reducing the size of the uterus following delivery?
A. progesterone
B. prostaglandin
C. oxytocin
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DHEAS travels from the fetal adrenal cortex to the placenta where it is converted into oxytocin.
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Cortisol from the fetal adrenal gland will stimulate maturation of the lungs and production of surfactant.
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Blood within the umbilical ___________ contain(s) high concentrations of fetal waste products.
arteries
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A ball of about eight cells formed about 50 to 60 hours after fertilization is called a
A. zygote.
B. morula.
C. blastocyst.
D. embryo.
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The progressive fusion of the acrosomal membrane with the plasma membrane of the sperm is called the
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After meiosis I in males, ________ are formed.
A. primary spermatocytes
B. secondary spermatocytes
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Hypocalcemia enhances the excitability of nerves and muscles because of the ____ permeability of the cell membrane to ___.
A. increased, K+
B. decreased, K+
C. increased, Na+
D. decreased, Na+
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Cells synthesizing hydroxyapatite in bones are termed as
A. osteoblasts.
B. osteoclasts.
C. osteocytes.
D. osteosarcoma cells.
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Bone resorption is produced by the action of _____________, which return bone calcium and phosphate to the blood.
A. osteoblasts
B. osteoclasts
C. osteocytes
D. calcitonin